1838–1913, American surgeon and librarian, b. Indiana. In the Civil War he was medical inspector of the Army of the Potomac. After the war he was given charge of the Surgeon General's Library in Washington. The catalog entries greatly increased under his supervision by 1873, and soon after he began work on the great Index Catalogue. Sixteen volumes appeared before his military retirement. In 1879 he initiated the Index Medicus, a monthly guide to current medical literature. Billings designed plans for the construction of Johns Hopkins Hospital. His essays on hospital administration and training remain classics. Under his librarianship (1864–95) the National Library of Medicine became one of the greatest medical library systems in the world. In 1889 he compiled the National Medical Dictionary. As director of the combined Astor, Lenox, and Tilden foundations in New York City, which were to become the New York Public Library, he consolidated the collections, planned and supervised the erection of the central library building, united the various free circulating libraries of the city, secured $5 million from Andrew Carnegie for branch buildings, and in general created the New York Public Library as it now stands. It was at Billings' suggestion that punched card machinery was developed, forming the beginnings of computer technology. He also supervised compilation of U.S. census information in 1880 and 1890.

See his Selected Papers (comp. with a biography by Rogers, F. B. , 1965);.